The design of the fixture of the arc lathe with turning instead of milling

The design of the fixture of the arc lathe with turning instead of milling

The bushing of a certain product part (the insert in the nylon gear of an automobile) has 3 R20mm arcs on the circumference, as shown in Figure 1. This arc can prevent the shaft sleeve from rotating when the nylon gear is working. In the past, the arc was usually processed by a milling machine. The parts were clamped on the indexing head and processed with a φ 40mm end mill, which was time-consuming and laborious for indexing, which was not only inefficient. , Also affects the production cycle. In order to solve this problem, a set of lathe fixtures was designed, and the milling arc processing was changed to turning arc processing, which increased the efficiency by more than 4 times and met the urgently needed requirements of production.

　　1. The structure and working principle of the lathe fixture

　　The lathe fixture used for turning the arc is shown in Figure 2. Four positioning pins are distributed on the circular fixture body, and the workpiece is sleeved on it. In order to prevent the workpiece from rotating when the first arc is turned, drill a φ2.9 (+0.1-0) mm process hole on the workpiece with a drilling jig, as shown in Figure 3, φ2.9 (+0.1-0) mm process hole Set it on the φ2.8 (0--0.015) mm round pin to limit the rotation of the workpiece. After pressing with a shoulder nut, turn the first arc on the workpiece to ensure that the size is φ40 (+0.1-0) mm. Then, loosen the shoulder nut, rotate the workpiece, and close the already turned arc to the φ2.8 (0--0.015) mm round pin, as shown in Figure 4, to achieve the indexing arc angle and prevent turning during turning The role of workpiece rotation. After tightening the nut to compress the workpiece, turn the second arc, and so on, so that the turning process of 4 workpieces and 3 places R20mm is completed.

　　2. Determination of the position of the positioning pin

　　According to the situation that the workpiece is rotated counterclockwise around the positioning pin after being subjected to the cutting force, consider that the φ2.9 (+0.1-0) mm process hole should be processed in the subsequent turning arc. In order not to affect the final shape of the workpiece and meet the drawing requirements, And considering the area of the arc and the size of the process hole and other factors, after the final comprehensive analysis, the position of the round pin is determined to be (22±0.02) mm and (7±0.015) mm, as shown in Figure 

　　3. Conclusion

　　The lathe fixture not only solves the problem of low arc milling efficiency, but also solves the measurement problem during arc processing, and also realizes multi-piece clamping and multi-piece processing, which greatly improves production efficiency. Practice has proved that the fixture is easy to use and has stable performance, and is highly praised by operators.